got it, thank for your help. I started to write some documentation some time ago, and the answer was http://wiki.nethserver.org/doku.php?id=howto:useful_commands#join_the_domain
[root@leo lsd]# realm join -U administrator stephdl.dyndns.org
Password for administrator:
[root@leo lsd]# realm list
stephdl.dyndns.org
type: kerberos
realm-name: STEPHDL.DYNDNS.ORG
domain-name: stephdl.dyndns.org
configured: kerberos-member
server-software: active-directory
client-software: sssd
required-package: oddjob
required-package: oddjob-mkhomedir
required-package: sssd
required-package: adcli
required-package: samba-common-tools
login-formats: %U@stephdl.dyndns.org
login-policy: allow-realm-logins
Please @everybody, write your knowledge to the wiki